The present invention relates generally to aerodynamics and, more particularly, to a reconfiguration control system for optimizing the spanwise lift distribution on a blended wing-body aircraft by reconfiguring the deflection of trailing edge control surfaces.
There are primarily two types of aircraft configurations: the more common configuration which includes a tail section comprised of vertical and horizontal stabilizers located at the aft end of a tubular fuselage; and the tailless configuration. As to tailless aircraft, there are two sub-types: a first type which has no central body, commonly known as a “flying wing,” and a second type having a central body which is blended into laterally extending wings.
Tailless aircraft possess the advantages of inherently lower weight and drag than a comparatively sized conventional aircraft having a fuselage and tail section. Several features of tailless aircraft effect these advantages. First, the need to enclose payloads in the wing results in thicker airfoil sections that are efficient at resisting bending loads, thereby lowering the necessary structural weight. Second, payload and fuel are distributed in the spanwise direction, which shifts the weight closer to where the lift is generated, thus reducing the structural loads that must be carried. Third, elimination of horizontal and vertical tail surfaces reduces the aircraft's wetted area and thus reduces parasite (skin friction) drag. These advantages have enticed aircraft designers to consider tailless configurations for a variety of military and commercial applications.
Tailless aircraft have several shortcomings that have frustrated those who seek to realize the significant advantages offered by this design. Because tail moment arms (the distance between the control surfaces and the center of gravity) are shorter, greater changes in local lift may be required to trim the airplane through different flight conditions. Deflecting control surfaces to trim the aircraft usually changes the spanwise lift distribution in a way that increases induced drag (drag from vortical energy imparted to the air in the process of generating lift).
Furthermore, tailless aircraft are more sensitive to shifts in location of the center of gravity along the longitudinal axis than are conventional aircraft having fuselages and tail sections. A shift in the center of gravity could be caused during flight by the use and transfer of fuel or by the movement of passengers and cargo. While conventional aircraft adjust to shifts in center of gravity with minimal change in wing lift distribution and drag characteristics, tailless aircraft require substantial changes in lift distribution that have a corresponding impact on drag. This presents a somewhat intractable problem that has impeded the development of a commercial airliner having a tailless design.
Based on the foregoing, it can be appreciated that there presently exists a need for a tailless aircraft which overcomes the above described shortcomings of the tailless aircraft of the prior art and which enhances the aerodynamic and weight advantages inherent to a tailless design. The present invention fulfills this need in the art.